The present embodiment relates generally to a treating fluid, particularly a spacer fluid for introduction into a subterranean zone penetrated by a wellbore.
A spacer fluid is a fluid used to displace one “performance” fluid in a wellbore before the introduction into the wellbore of another performance fluid. For example, while drilling oil and gas wells, one performance fluid, such as an oil-based or water-based drilling fluid, is circulated through the string of drill pipe, through the drill bit and upwardly to the earth surface through the annulus formed between the drill pipe and the surface of the wellbore. The drilling fluid cools the drill bit, lubricates the drill string and removes cuttings from the wellbore. During the drilling process, the drilling fluid dehydrates or loses filtrate to the formation so that the fluid remaining in the annulus gels or increases in viscosity and a layer of solids and gelled drilling fluid known as filter cake is deposited against the formation face.
When the desired drilling depth of the well is reached, another performance fluid, such as a slurry containing a cement composition, is pumped into the annular space between the walls of the wellbore and pipe string or casing. In this process, known as “primary cementing,” the cement composition sets in the annulus, supporting and positioning the casing, and forming a substantially impermeable barrier, or cement sheath, which isolates the casing from subterranean zones. It is understood that the bond between the set cement composition and the wellbore is crucial to zonal isolation.
However, the increase in viscosity of the drilling fluid and deposit of filter cake are detrimental to obtaining effective drilling fluid displacement and removal from the walls of the wellbore and a subsequent competent bond between casing, primary cement and the walls of the wellbore. Incomplete displacement of the drilling fluid often prevents the formation of an adequate bond between the cement, the casing or pipe and the wellbore.
In addition, when pumping various fluids into a wellbore, it is important to make sure that they do not adversely affect the properties of other fluids in the wellbore. It is understood that such fluids having adverse reactions with each other are referred to as being “incompatible.”
Spacer fluids are often used in oil and gas wells to facilitate improved displacement efficiency when pumping new fluids into the wellbore. Spacer fluids are typically placed between one or more fluids contained within or to be pumped within the wellbore. Spacer fluids are also used to enhance solids removal during drilling operations, to enhance displacement efficiency and to physically separate chemically incompatible fluids. For instance, in primary cementing, the cement slurry is separated from the drilling fluid and partially dehydrated gelled drilling fluid is removed from the walls of the wellbore by a spacer fluid pumped between the drilling fluid and the cement slurry. Spacer fluids may also be placed between different drilling fluids during drilling fluid change outs or between a drilling fluid and a completion brine.
While the preferred embodiments described herein relate to spacer fluids and cement compositions, it is understood that any treating fluids such as drilling, completion and stimulation fluids including, but not limited to, drilling muds, well cleanup fluids, workover fluids, conformance fluids, gravel pack fluids, acidizing fluids, fracturing fluids and the like can be prepared using zeolite and a carrier fluid. Accordingly, improved methods of the present invention comprise the steps of preparing a wellbore treating fluid using a carrier fluid and zeolite, as previously described herein, and placing the fluid in a subterranean formation.
Therefore, treating fluids that have beneficial rheological properties and are compatible with a variety of fluids are desirable.